Electric heater apparatus



2 Sheets-Sheet 1 DAMAGED N FINISH 6 OLD TYPE TUBULAR HEATER 7 P. STILI-ER ELECTRIC HEATER APPARATUS RIM 4 March l0, 1970 Filed Aug. l, 1966 one-Place sTovE ToP 2 ANNuLAn conusn s ANNuLAn FLANGE s March l0, 1970 P. STILLER ELECTRIC HEATER APPARATUS 2 Sheets-Sheet 2 Filed Aug. 1. 1966 United States Patent O 3,500,018 ELECTRIC HEATER APPARATUS Paul Stiller, Scarsdale, N.Y., assignor to Teledyne Inc., Los Angeles, Calif., a corporation of Delaware Filed Aug. 1, 1966, Ser. No. 569,249 Int. Cl. H05b 3/68 U.S. Cl. 219-443 9 Claims ABSTRACT 0F THE DISCLOSURE Electric surface heater apparatus having particular utility with one-piece stove top apparatus is provided in accordance with an embodiment of this invention wherein the convolute portions thereof exhibit a select temperature differential whereby the inner portions thereof radiate rather intense heat while the outer portions thereof have a reduced heat output to thereby increase the efficiency of the heater apparatus and protect the finish of any surface mount provided therefor.

This invention relates to electric heater apparatus, and more particularly to tubular electric surface heater suitable for use in an electric range or stove having a onepiece top of known for-m.

Until recently, the two-piece stove top, as exemplified by U.S, Letters Patent No. 3,054,882 to Altman and Stiller, as issued on Sept. 18, 1962, constituted one of the prime types of stove top construction in wide use within the United States. As illustrated therein, such construction generally included a unitary range platform having suitable heater openings formed therein and appropriate trim rings adapted to mount Within said heater openings and shield the porcelain finish of the unitary range platform in the area of said heater openings from the intense heat radiated by the heater operatively positioned within said heater openings. Thus, in addition to the plurality of obvious functional attributes possessed by such trim rings, they also served to preserve the finish and hence the longevity of stove tops formed in accordance with such two-piece construction. Recently, however, the so-called one-piece cooking platform or stove top has become popular due to both its inherently cheaper structural design and its aesthetically pleasing appearance which atracts many purchasers thereof. The construction of the one-piece stove top is similar to the twopiece construction mentioned above, however, the trim rings are omitted whereby the containergmeans to be heated is nested directly on the heater in convolute form. In this case, however, as the trim rings are omitted, their function in acting to preserve the finish and longevity of the stove tops so formed have also been lost. Accordingly, relatively new one-piece -stove tops, much to the chagrin of purchasers who selected this type of construction for its aesthetically pleasing appearance, quickly begin to show signs of cracking, crazing and discoloration in the unprotected areas of the porcelain finish surrounding the heater openings thereof due to the intense heat radiated by the convolute heater positioned therein. Furthermore, as such intense heat is radiated by the convoluted heater is in no Way shielded from the one-piece stove top, the one-piece stove top soon attains uncomfortably high working temperatures whereby substantial disadvantages in use soon become apparent to such purchasers.

Therefore it is a primary object of this invention to provide electrical surface heater apparatus, particularly adapted for use in conjunction with one-piece stove top apparatus, which reduces the consumption of electrical current and additionally preserves the finish of its surface mount due to a reduction in the amount of heat radiated thereto. Various other objects and advantages of the invention will become clear from the following detailed description of an exemplary embodiment disclosed herein, and the novel features will :be particularly pointed out in connection with the appended claims.

In accordance with the invention, electrical surface heater apparatus is provided wherein the convolute positions thereof exhibit a select temperature differential whereby the inner portions thereof radiate rather intense heat while the outer portions thereof have a reduced heat output to thereby increase the efficiency of the heater apparatus according to this invention and protect the finish of any surface mount provided therefor. The invention will be more clearly understood by reference to the following detailed description of an embodiment thereof in conjunction with the accompanying drawings in which:

FIG. 1 shows conventional one-piece stove top apparatus without a trim ring and a prior art surface heater mounted therein that has Wasted its heat into said top and damaged the porcelain finish thereof;

FIG. 2 is a top view of an embodiment of the surface heater apparatus in accordance with the teachings of this invention as mounted in a one-piece stove top apparatus;

FIG. 3 is a cross section along the axis line 3-3- of the FIG. 2 embodiment of this invention which serves to demonstrate the heating eliiciency thereof; and

FIG. 4 is an enlarged view of the ring portion 4 of the embodiment of this invention depicted in FIG. 2.

Referring now to the drawings and more particularly to FIG. 1 therefor, there is shown a conventional onepiece `stove top having electrical surface heater apparatus mounted therein which is commonly in use today. As shown in FIG. 1, the depicted apparatus includes a onepiece stove top 2, which may be die-formed to provide a at working and cooking surface and electric heater apparatus in convolute form mounted therein. The onepiece stove top 2 includes an open annular corner 3 having a down-turned annular rim 4 and an annular flange `5 formed therein for supporting the electric heater apparatus 7 to thus define a surface heater opening in said one-piece stove top 2. The electric heater apparatus 7 comprises the conventional tubular metallic heating sheath 7 in convolute form wherein each of the convolute circles 7 have the same heat output.

The cracking, crazing, and the discoloring, marked damaged finish 6 in FIG. 1, is caused by the intense heat radiated by the tubular metallic heating sheath 7 and more particularly that dissipated by the outer convolute portion 7a into the annular corner 3 and rim 4. This intense heat is radiated from the outer convolute portion 7a into the stove top 2, to thereby ruin the porcelain finish in the manner indicated as well as to waste the heat unit dissipated thereby for cooking purposes. Moreover, the entire stove top attains an uncomfortably high working temperature. Accordingly, it will be seen that conventional electric surface heater apparatus in combination with one-piece stove top apapratus as illustrated by FIG. l, provide an inefficient and disadvantageous arrangement whose pleasing appearance is Isoon marred.

An embodiment of the electrical surface heater apparatus in accordance with this invention is shown in FIGS. 2-4 in combination with one-piece stove top apparatus. As shown, most clearly in FIG. 2, this embodiment of the surface heater apparatus according to the present invention comprises a multi-circle convolute heating element which principally includes a single outer circle convolute portion 10 and an inner con-volute portion including a plurality of circles 11. The single outer circle convolute portion 10 has a low intensity heat output which Vmay be approximately 300 watts as indicated while, in contrast thereto, the inner convolute portion which includes a plurality of inner circles 11 has a high intensity heat output of approximately 1200y watts.

The single outer and the two inner circles 10 and 11 respectively, forming the multicircle convolute heating element terminate in two sheathed legs 12 mounted in a molded die-electric terminal block 13 at the rear side of the stove. Electric power wires (not shown) are connected to the block 13 for heating the circles 10 and 11 to their respective working differential temperatures.

As is shown most clearly in FIGS. 2 and 4, the heater apparatus in accordance with this invention includes in the center portion thereof a unitary and continuous heating coil HC having a first constant pitch angle in the single circle outer convolute portion 10 for providing the previously mentioned low intensity heat adjacent the one-piece stove top apparatus to thereby avoid damage to the porcelain finish as indicated at 6 (FIG. 1). The second and a second constant pitch angle in the plurality of circles 11 making up the inner portion of the convolute heating element pitch angle of the heating coil HC constitutes a closely spaced pitch angle for providing the aforementioned 1200 watt heat intensity enabling high intensity heat to be applied to both small and large diameter cooking pots as illustrated in FIGURE 3. As may be seen by inspection of FIGURE 2 or 4, only once and the depicted arrangement of the convolute circle portions.

10 and 11, with its single dual pitch heating coil HC is simple to manufacture. Furthermore, its utility is enhanced by reason of its efficiency in distributing the heat where needed and radiation losses are reduced to a minimum. In addition, the assembly of the heater apparatus in accordance with this invention does not require electric switches for controlling the current flow to select convolute portions as do most prior art heater apparatus, having separate and independent electrically wired convolutes portions.

The surface heater apparatus according to this invention, as shown in FIG. 2, is mounted within the onepiece stove top on a support 14, known in the art as a spider. The spider 14 comprises metallic bars or arms, four of which are shown in the general form of a cross. The rear end of one spider arm 14 has a foot 1S which bears down upon one of the terminal legs 12 of the heater sheath so that this and other fastening means hold the surface heating apparatus firmly seated against the top edges of the four spider arms 14 in the manner well known to those of ordinary skill in the art.

As shown in FIGS. 2 and 3, the outer ends of the four spider arms 14 are seated down within the rim 4 and rest upon the ange of the one-piece stove top 2 so that the top surface of the surface heater apparatus according to the instant invention is in a common plane, having a fractional clearance above the plane of the flat Working surface of the one-piece stove top 2.

This arrangement places the single circle outer portion of the convolute heating element adjacent to the annular corner 3 and rim 4 which are the critical portions of the one-piece stove top most susceptible to damage. Accordingly, it will be seen that only the low heat intensity of the single circle 10 outer portion of the convolute heating element is applied to these heater opening'portions whereby they are not scorched or burned so that damage is not initiated in the porcelain and hence the scorching and crazing cannot spread to the Working surface of the one-piece stove top.

In addition, it appears that the minimum temperature of the single circle, outer portion 10 of the convolute heating element induces ventilation across the annular corner 3 and along the rim 4. This further feature serves the important function of maintaining the area of the stove top 2 at a low and comfortable working temperature, thus minimizing heat radiation from the electrically heated. stove into the kitchen atmosphere.

4 What is claimed is: 1. Electric surface heater aparatus comprising: tubular heating sheath means, said tubular heating sheath means being formed in the shape of a flat spiral having a plurality of curvilinear portions in a common plane, said curvilinear Iportions including a large external portion defining the outermost extent of said flat spiral and smaller curvilinear portions within the confines and approximate central of said external portion; unitary heating resistance means helically wound within said tubular heating sheath means and insulated therefrom, said helical winding of said unitary heating resistance means including a first section having a relatively low number of turns per unit length and a second section having a relatively high number of turns per unit length, said first section of said helical winding being wound within said large external portion and said second section of said helical winding being wound within smaller curvilinear portions of said flat spiral whereby said external portion is adapted to receive relatively low intensity heat and the remainder of said smaller curvilinear portions of said fiat spiral is adapted to receive relatively high intensity heat; means adapted to receive electrical energy and to apply the same to said unitary heating resistance; and

means for 4mounting said tubular heating sheath means in enclosure means having a protective finish thereon so that a surface of said tubular heating sheath means is exposed therefrom and said large external portion of said tubular heating sheath means is substantially proximate a portion of said enclosure means while said smaller curvilinear portions of said tubular heating sheath means are remotely located therefrom.

2. The apparatus of claim 1 wherein said tubular heating sheath means has a substantially uniform inside and outside diameter throughout the length thereof.

3. The apparatus of claim 1 wherein said first section of said helical winding of said unitary heating resistance means has a first substantially uniform pitch and said second section of said helical winding of said unitary heating resistance means has a second substantially uniform pitch.

4. The aparatus of claim 3 wherein said tubular heating sheath means has a substantially uniform inside and outside diameter throughout the length thereof.

5. Electric stove apparatus comprising:

one-piece stove top means having a porcelain finish and at least one apertured portion therein for receiving electric heater means, said at least one apertured portion of said one-piece stove top means being defined by a downwardly formed annular rim in said one-piece stove top means which includes both an annular corner and an annular flange; and

electric heater means mounted in said at least one apertured portion and supported on said annular flange, said electric heater means comprising;

tubular heating sheath means, said tubular heating sheath means being formed in the shape of a fiat spiral having a plurality of curvilinear portions in a common plane, said curvilinear portions including a large external portion defining the outermost extent of said flat spiral and smaller curvilinear portions within the confines and approximately central of said external portion,

unitary heating resistance means helically wound Within said tubular heating sheath means and insulated therefrom, said helical winding of said unitary heating resistance means including a first section having a relatively low number of turns per unit length and a second section having a relatively high number of turns per unit length, said rst section of said helical winding being wound within said large external portion and said second section of said helical winding being wound within said smaller curvilinear portions of said fiat spiral whereby said external portion is adapted to receive relatively low intensity heat and the remainder of said smaller curvilinear portions of said at spiral is adapted to receive relatively high intensity heat, and

means adapted to receive electrical energy and to apply the same to said unitary heating resistance means.

6. The apparatus of claim 5 wherein said tubular heating sheath means has a substantially uniform inside and outside diameter throughout the length thereof.

7. The apparatus of claim 5 wherein said rst section of said helical winding of said unitary heating resistance means has a first substantially uniform pitch and said second section of said helical winding of said unitary heating resistance means has a second substantially uniform pitch.

8. The apparatus of claim 7 wherein said tubular sheath means has a substantially unform inside and outside diameter throughout the length thereof.

References Cited UNITED STATES PATENTS 2,557,832 `6/1951 McCormick 219-392 2,831,100 4/1958 Kelly 219-463 3,004,132 10/1961 Harris et al. 219-461 2,811,097 10/1957 Theisen 219-336 1,555,543 9/1925 Ziola 219--468 2,290,901 7/ 1942 Weinhardt et al. 219-552 G. HARRIS, Primary Examiner 20 F. E. BELL, Assistant Examiner 

